Why did the mail go out and the other party received spam?

When the mail is sent out, the other party receives spam for the following reasons:

The email sent by 1. contains sensitive words, and the other party's mailbox automatically defaults to spam. The solution is to purify the right button and avoid sensitive words.

2. There is something wrong with the spam interception protocol level of the other mailbox, or it is operated. The solution is: select this spam and choose that it is not spam. (The following is a demonstration of QQ mailbox)